The present invention relates to line coupling apparatus in a log-hauling system, and particularly, to apparatus which is commonly referred to as a butt hook and which forms part of the rigging in a high-lead log-hauling system.
The usual high-lead log-hauling system employs a main line and a haulback line which are joined to form a line loop extending between a tower and a remote pulley station The two lines in the loop are joined by a butt rigging assembly having generally one or more butt chains, each of which is equipped with a butt lock at its free end. A choker line terminating at a nubbin, or ferrule, is releasably coupled to the line loop by releasable attachment of the line nubbin to a butt lock in the butt rigging assembly. The position of the assembly between the tower and the pulley station is controlled by a yarder located near the tower.
The usual type of butt lock known in the prior art includes an elongate body provided with an upper opening and a lower nubbin seat The upper opening is of a size enabling passage of the choker nubbin and attached line therethrough, in a line-axial direction substantially normal to the body axis. The nubbin is placed in a seated position by pulling the choker line in a generally downwardly direction through a lower opening in the lock. Likewise, the line is released from the lock by feeding the line upwardly through the lower opening in the lock, to unseat the nubbin, then drawing the line, again in a direction substantially normal to the body axis, through the upper opening in the lock in a line-axial direction.
A characteristic feature of prior art butt locks of the type described above is that the choker line nubbin is captured in the lock only when the choker line is under tension. When the line is slack, as during a log loading or unloading operation, line coiling may cause the line to be fed upwardly through the lock's lower opening, thereby unseating the nubbin, and placing the line in a "pre-release" position. When tension is reapplied to the choker line, the line may be pulled through the lock's upper opening, detaching the line from the lock, or the line may be kinked as the nubbin is pulled into the nubbin seat. In addition to these problems, the free end portion of the choker line, which is fed through the lock's lower opening when the line is slack, tends to become snagged on vegetation, and may also present a safety hazard.
A general object of the present invention is to provide, for use as a butt lock in a log-hauling system, a line coupling apparatus which substantially overcomes above-mentioned problems associated with butt locks known in the prior art.
A more particular obJect of the invention is to provide such an apparatus which functions to prevent a choker line nubbin, once attached to the apparatus, from becoming released inadvertently when the choker line is slack.
Another object of the invention is to provide such apparatus in which nubbin release requires initial axial movement toward a release position placement of a swingable shackle in the apparatus to a selected angular position, and withdrawal of the nubbin in a direction substantially normal to the choker line axis.
The apparatus of the present invention includes an elongate body having an axially extending chamber of a size enabling axial movement of a choker nubbin therein between upper and lower positions through a constriction of substantially clearance fit. The choker nubbin and adjacent portions of choker line are receivable in the chamber by passage, in a direction substantially normal to the choker line axis, through an elongate keyhole slot formed in the body. The apparatus is linked in a butt chain by a shackle which is mounted on the upper body end for swinging toward and away from a position of axial alignment with the body. A plate formed on the shackle acts to block passage of the choker through the keyhole slot at all shackle positions except a preselected one which is remote from the aligned position.
In a preferred embodiment of the invention, the shackle swings about an axis which substantially parallels the direction of movement of the choker line and nubbin through the keyhole slot. The shackle plate has a notch which is alignable with the slot at a position intermediate its aligned position and an extreme pivoted shackle position.
These and other objects and features of the present invention will become more fully apparent when the following detailed description of preferred embodiments of the invention is read in conjunction with the accompanying drawings.